Compounding and vulcanization of synthetic rubber



Pa ma/Mt 1,1040- UNITED". STATES PATENT OFFICE I COMPOUNDING m vuncmzs'rrou or SYNTHETIC RUBBER Albert A. Somervllle, Game], 8. 2., assinor to B. T. Vanderbilt Company, 1110., New York,

N. Y., a corporation of New York 4 Claims.

My invention relates to improvements in the compounding and vulcanization oLsynthetic rubf bers produced by copolymerization oi butadiene and styrene. Synthetic rubbers of this type are illustrated by the copolym'er product currently, designated Git-S rubber. In my application Serial No. 522,785,1lled February 1'1 1944, I have described my discovery that appropriate additions 01' copper, suchor as appropriate compounds, to compounds at this type of ynthetic rubber ailords important improvements with respect to rate 01! cure and variability, particularly in rate or cure, when these compounds are vulcanized with sulfur, as such, inamount exceed- I ing that required to form cuprlc suliide with the copper present. I have found that copper is with advantage added to compounds of such synthetic rubber, in applying my discovery, as a copper salt of a dialkyldithiocarbamic. acid such as copper dimethyldithiocarbamate, copper diethyldithio-- carbamate, or copper dibutyldithiocarbamate.

I Dispersion of the copper in the compound is thus promoted and particles or metallic copper areeliminated as'a constituent oi the compound. I have also i'oundthat these copper salts appar- No Drawing. Application February 11, 1044.

-. Serial No. mass break under "it," and for hore hardness under H. H 1

The acceleration in rate of cure will be apparent from a comparisonot the-yalues (or stress at 300% elongation and for tensile strength and the ently are activators of other vulcanization accelerators, particularly zinc salts or the dialkyldithiocarbamic was, in compounds 0! this type of synthetic rubber. o r

The following examples will illustrate the prac-- tice oi my'inventi nd include comparisons inpercentage elongation at break particularly for the 5 and 10 minute cures. The comparison of these values as between Example I! and Example I illustrates the improvement to be secured as dedicating somefor' it's'advantaaes. the tabula- I tions of these compounds, cures and physical properties, the compound of each example was Image upoi the number oiparts by weight indifloated opposite each designated component,- the cures were in a platen press for the periods 7 cated inhalant at. the'lei't under the temperature, 1 1 the cures'in' the group ei'l'ected at the temperature, and. for each periodot cure-the values for stress at 300% e1on-' gation in pounds per square inch appear under r "S," for tensile strength in pounds per square inch under '1'. for percentage elongation at scribed in my concurrently filed application above identified. The comparison of these values 'as between Example In and Example II will show the further improvement secured by my present invention. InExample I. the values for stress mat 300% elongation and the tensile strength are wellsdeveloped in 0 minutes and the values for j stress at 300% elongation and the percentage elongation at break for the 10 minute and longer cures show that over curing has set in before 10 minutes. I ior example, in Example III.the perccntase' elonsation at break reached a value in 10 minutes which had not been attained, in Example II. in 20 Again, therelative values for stress at 300% elongation and tensile strensth attained in 15 minutes in Example III were atsuch copper salts.

tained in something less than-30 minutes in Example IL The proportion of sulfur used is not critical and may follow conventional practices providing it is added to the compound subjected to vulcanization in amount exceeding that required to combine with the added copper to form cupric sulfide as described in my concurrently flied application previously identified.

The plasticizer used in the foregoing examples was a mixture of 15 rte by weight of a petroleum sulfonate, 5 parts of normal butyl alcohol and 80 parts of a viscous petroleum oil (currently sold i vulcanized copolymer of butadiene and styrene containing sulfur and a copper salt of a dialkyldithiocarbamic acid and the product of vulcanization of such copolymer compounds containing My invention also includes such vulcanizable but unvulcanized compounds containing sulfur and a copper salt of a dialkyldithiocarbamic acid as activator particularly of a zinc salt of a dialkyldithiocarbamic acid and the product of vulcanization of such copolymercompounds containing such copper salts.

I claim: i

1. A vulcanizable compound comprising a rubher-like copolymer or butadiene and styrene, a copper salt oi a dialkyldithiocarbamic acid in a quantity sufllcient to accelerate the rate of cure upon vulcanization of the compound, and an amount 01' suliur exceeding the amount required to convert all of the copper in the copper salt to cupric sulfide.

2. The product of the vulcanization of the compound of claim 1. p

3. A vulcanizable compound comprising a rubher-like copolymer of butadiene and styrene, a zinc salt of a dialkyldithiocarbamic acid in a quantity sufllcient to accelerate the rate of cure upon vulcanization of the compound, a copper salt of a dialkyldithiocarbamic acid as an activator of the zinc salt, and an-amount of sulfur exceeding the amount required to convert all of the copper in the copper salt to cupric sulfide.

'4. The product of the vulcanization of the compound of claim 3.

ALBERT A. SOMERYILLE. 

